Alpha-1 adrenergic drugs have recently shown great potential in the treatment of BPH. The existence of receptor heterogeneity within the alpha-1 adrenoceptors suggests the possibility of improving drugs by refining their subtype selectivity. Molecular cloning of three subtypes of the a1 receptors has made it possible to construct cell lines containing individual human alpha-1 adrenergic receptors for use in drug discovery. However, the use of such "heterologous expression systems" in drug development is impeded by the paucity of information available on the types of G-proteins present in host cells chosen for transfection. These components play a key role in defining the pharmacological responses of these cells. During Phase I, host cells will be selected for transfection of human alpha-1 adrenergic receptors which can accurately reconstitute responses of native tissues. The G-protein content of a series of mammalian cell lines will be determined. This information will be used to guide the selection of potential transfection hosts containing appropriate signalling systems. The functional response properties of these heterologous expression systems will be determined and compared to native systems. In Phase II, the program will be expanded to encompass the remaining human a1 receptor subtypes and a broader array of tissues, cell lines and G-proteins.